American Airlines will add the first of 76 new Boeing jets to its fleet this week in a move that the carrier hopes will cut fuel and maintenance costs.

The Boeing 737-800 aircraft will replace about one-fourth of American's current aging fleet of McDonnell Douglas MD-80 series jets, which have been the subject of several maintenance problems in the past year.

American took delivery of the first two planes late last month, held a media open house Monday, and planned to put them into service carrying passengers Tuesday in Chicago.

The planes are the newest generation of Boeing's workhorse 737 series. American already has 77 Boeing 737-800s it bought nearly a decade ago. They list for $72.5 million to $81 million. American officials said they paid less than sticker price, but wouldn't say how much.

"This is a strategic investment for our future," said pilot Jim Kaiser as he stood in the aisle of a jet that still had that new-plane smell of leather, plastic and carpeting.

With air traffic down this year because of the recession, and financial markets in turmoil, airlines have had trouble getting financing for planes.

Mark Moessner, a corporate planning executive for American, a unit of AMR Corp., said the company had arranged backup financing - typically from the plane manufacturer - or sale-and-leaseback agreements to cover most of the new jets, which will arrive between now and the end of 2011.

The jets get 28 percent better mileage than the MD-80s they will replace - 35 percent more on a per-seat basis, when you consider they have 160 seats instead of the 140 on an MD-80, even though MD-80s are 18 feet longer.

The 737-800s have three seats on each side of the aisle in coach instead of the 2-3 layout of the MD-80s. American squeezed in two more rows in coach by placing rows closer together, using thinner seat padding and removing rear galleys.

The legroom was adequate for a person under 6-feet, but taller or larger passengers could be squeezed for space.

American also added some things not seen on its other planes; including two AC power outlets for every three seats in coach, larger overhead bins and 10-inch flat-screen TVs every few rows. American said it will eventually add Internet access as well.

Boeing has delivered more than 1,500 737-800s since 1998, but American was unable to buy any in recent years because of heavy losses and huge debt in the years after the 2001 terror attacks.

Instead, American continued to rely on its MD-80 series jets. It has about 270 - nearly half its 616-plane fleet. American got its first MD-80 in 1983, and the average age now is 19 years.

As those planes aged they faced more maintenance issues. Last year, American had to ground its entire MD-80 fleet to repack electrical wires, then the Federal Aviation Administration ordered the airline to inspect most of its MD-80s for possible cracks on overwing frames.

The new 737s "will have a 6-year honeymoon until they receive their first heavy check," or maintenance overhaul, Moessner said.